Test CRT 8XP4

[sylvania]

I was wondering if i did something wrong, I have a Sylvania chassis 336mu I hooked up this test CRT with yoke and anode connected brought up voltage slowly a bright spot formed on the CRT a pin sized area of phosphorous burned off in the middle pin sized i turned brightness down and shut it off. I am only getting a few pops out of speaker and no picture hooked to VCR. CRT glows and my HV is good,tubes checked ok and been recapped. I checked the test CRT for shorts and emissions tests like new.

[Electronic M]

If there is a bright spot in the center (and no light elsewhere on screen), then there is no horizontal or vertical deflection. Probably an open connection or two to the yoke. The horizontal section is clearly working or else there would not be enough HV for it to make any light on the CRT screen. The horizontal section may not work properly with no yoke in place (the HV may be wrong and it is probably not good for the circuits to run unloaded).

It is bad to run a CRT without deflection unless you can reduce the brightness enough....To prevent phosphor burn. Phosphor burn is when too much beam current (ie brightness) is applied to a spot on the phosphor. When it happens the energy burns off the phosphor and the spot never lights up again. Be thankful you only burned a test CRT (lots of them have that mark of use), and not the regular use CRT that will go in at the end of your resto. Note complete loss of deflection (both horizontal and vertical resulting in dot burn), and partial (vertical or horizontal resulting in a line of burn) can burn the phosphor. Always turn the brightness down to normal viewing brightness at brightest, and if that can't be done do not allow the screen to run that way for more than a few seconds at a time.

One question. Are you using the TVs factory yoke, or a yoke that came with the test tube? If you are not using the TV's yoke, then please try it.

[sylvania]

Thank You